A Ghostbuster is a person or even in a few cases a spirit itself that performs duties of removal of a spirit (aka: ghost, apparition, the undead). Officially the Ghostbusters are paranormal investigators, not ghosthunters. Catching ghosts just happens to be their primary form of business. Sometimes removal doesn't mean through means of weapons as a spirit may leave due to fulfillment, being remembered, or destruction of an object attaching them to this world. However, most hauntings are of unhappy spirits, and like humans may have negative reasons for being there.